package test.skymobi.http.file;

import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.handler.codec.http.*;
import io.netty.handler.stream.ChunkedFile;
import io.netty.util.CharsetUtil;

import javax.activation.MimetypesFileTypeMap;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.RandomAccessFile;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.text.SimpleDateFormat;
import java.util.*;
import java.util.regex.Pattern;

import static io.netty.handler.codec.http.HttpHeaders.Names.*;
import static io.netty.handler.codec.http.HttpHeaders.isKeepAlive;
import static io.netty.handler.codec.http.HttpHeaders.setContentLength;
import static io.netty.handler.codec.http.HttpMethod.GET;
import static io.netty.handler.codec.http.HttpResponseStatus.*;
import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;

public class HttpStaticFileServerHandler extends ChannelInboundHandlerAdapter {

    public static final String HTTP_DATE_FORMAT = "EEE, dd MMM yyyy HH:mm:ss zzz";
    public static final String HTTP_DATE_GMT_TIMEZONE = "GMT";
    public static final int HTTP_CACHE_SECONDS = 60;

    @Override
    public void channelRead(
            ChannelHandlerContext ctx, Object obj) throws Exception {

    	FullHttpRequest request = (FullHttpRequest) obj;
    	
        if (!request.getDecoderResult().isSuccess()) {
            sendError(ctx, BAD_REQUEST);
            return;
        }

        if (request.getMethod() != GET) {
            sendError(ctx, METHOD_NOT_ALLOWED);
            return;
        }

        final String uri = request.getUri();
        final String path = sanitizeUri(uri);
        if (path == null) {
            sendError(ctx, FORBIDDEN);
            return;
        }

        File file = new File(path);
        if (file.isHidden() || !file.exists()) {
            sendError(ctx, NOT_FOUND);
            return;
        }

        if (file.isDirectory()) {
            if (uri.endsWith("/")) {
                sendListing(ctx, file);
            } else {
                sendRedirect(ctx, uri + '/');
            }
            return;
        }

        if (!file.isFile()) {
            sendError(ctx, FORBIDDEN);
            return;
        }

        // Cache Validation
        String ifModifiedSince = request.headers().get(IF_MODIFIED_SINCE);
        if (ifModifiedSince != null && !ifModifiedSince.isEmpty()) {
            SimpleDateFormat dateFormatter = new SimpleDateFormat(HTTP_DATE_FORMAT, Locale.US);
            Date ifModifiedSinceDate = dateFormatter.parse(ifModifiedSince);

            // Only compare up to the second because the datetime format we send to the client
            // does not have milliseconds
            long ifModifiedSinceDateSeconds = ifModifiedSinceDate.getTime() / 1000;
            long fileLastModifiedSeconds = file.lastModified() / 1000;
            if (ifModifiedSinceDateSeconds == fileLastModifiedSeconds) {
                sendNotModified(ctx);
                return;
            }
        }

        RandomAccessFile raf;
        try {
            raf = new RandomAccessFile(file, "r");
        } catch (FileNotFoundException fnfe) {
            sendError(ctx, NOT_FOUND);
            return;
        }
        long fileLength = raf.length();

        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK);
        setContentLength(response, fileLength);
        setContentTypeHeader(response, file);
        setDateAndCacheHeaders(response, file);
        if (isKeepAlive(request)) {
            response.headers().add(CONNECTION, HttpHeaders.Values.KEEP_ALIVE);
        }

        // Write the initial line and the header.
        ctx.write(response);

        // Write the content.
        ChannelFuture writeFuture = ctx.write(new ChunkedFile(raf, 0, fileLength, Integer.MAX_VALUE));

        // Decide whether to close the connection or not.
        if (!isKeepAlive(request)) {
            // Close the connection when the whole content is written out.
            writeFuture.addListener(ChannelFutureListener.CLOSE);
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        if (ctx.channel().isActive()) {
            sendError(ctx, INTERNAL_SERVER_ERROR);
        }
    }

    private static final Pattern INSECURE_URI = Pattern.compile(".*[<>&\"].*");

    private static String sanitizeUri(String uri) {
        // Decode the path.
        try {
            uri = URLDecoder.decode(uri, "UTF-8");
        } catch (UnsupportedEncodingException e) {
            try {
                uri = URLDecoder.decode(uri, "ISO-8859-1");
            } catch (UnsupportedEncodingException e1) {
                throw new Error();
            }
        }

        if (!uri.startsWith("/")) {
            return null;
        }

        // Convert file separators.
        uri = uri.replace('/', File.separatorChar);

        // Simplistic dumb security check.
        // You will have to do something serious in the production environment.
        if (uri.contains(File.separator + '.') ||
                uri.contains('.' + File.separator) ||
                uri.startsWith(".") || uri.endsWith(".") ||
                INSECURE_URI.matcher(uri).matches()) {
            return null;
        }

        // Convert to absolute path.
        return System.getProperty("user.dir") + File.separator + uri;
    }

    private static final Pattern ALLOWED_FILE_NAME = Pattern.compile("[A-Za-z0-9][-_A-Za-z0-9\\.]*");

    private static void sendListing(ChannelHandlerContext ctx, File dir) {
        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK);
        response.headers().add(CONTENT_TYPE, "text/html; charset=UTF-8");

        StringBuilder buf = new StringBuilder();
        String dirPath = dir.getPath();

        buf.append("<!DOCTYPE html>\r\n");
        buf.append("<html><head><title>");
        buf.append("Listing of: ");
        buf.append(dirPath);
        buf.append("</title></head><body>\r\n");

        buf.append("<h3>Listing of: ");
        buf.append(dirPath);
        buf.append("</h3>\r\n");

        buf.append("<ul>");
        buf.append("<li><a href=\"../\">..</a></li>\r\n");

        for (File f : dir.listFiles()) {
            if (f.isHidden() || !f.canRead()) {
                continue;
            }

            String name = f.getName();
            if (!ALLOWED_FILE_NAME.matcher(name).matches()) {
                continue;
            }

            buf.append("<li><a href=\"");
            buf.append(name);
            buf.append("\">");
            buf.append(name);
            buf.append("</a></li>\r\n");
        }

        buf.append("</ul></body></html>\r\n");

        response.content().writeBytes(Unpooled.copiedBuffer(buf, CharsetUtil.UTF_8));

        // Close the connection as soon as the error message is sent.
        ctx.write(response).addListener(ChannelFutureListener.CLOSE);
    }

    private static void sendRedirect(ChannelHandlerContext ctx, String newUri) {
        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, FOUND);
        response.headers().add(LOCATION, newUri);

        // Close the connection as soon as the error message is sent.
        ctx.write(response).addListener(ChannelFutureListener.CLOSE);
    }

    private static void sendError(ChannelHandlerContext ctx, HttpResponseStatus status) {
        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, status);
        response.headers().add(CONTENT_TYPE, "text/plain; charset=UTF-8");
        response.content().writeBytes(Unpooled.copiedBuffer(
                "Failure: " + status.toString() + "\r\n",
                CharsetUtil.UTF_8));

        // Close the connection as soon as the error message is sent.
        ctx.write(response).addListener(ChannelFutureListener.CLOSE);
    }

    /**
     * When file timestamp is the same as what the browser is sending up, send a "304 Not Modified"
     *
     * @param ctx Context
     */
    private static void sendNotModified(ChannelHandlerContext ctx) {
        HttpResponse response = new DefaultHttpResponse(HTTP_1_1, NOT_MODIFIED);
        setDateHeader(response);

        // Close the connection as soon as the error message is sent.
        ctx.write(response).addListener(ChannelFutureListener.CLOSE);
    }

    /**
     * Sets the Date header for the HTTP response
     *
     * @param response HTTP response
     */
    private static void setDateHeader(HttpResponse response) {
        SimpleDateFormat dateFormatter = new SimpleDateFormat(HTTP_DATE_FORMAT, Locale.US);
        dateFormatter.setTimeZone(TimeZone.getTimeZone(HTTP_DATE_GMT_TIMEZONE));

        Calendar time = new GregorianCalendar();
        response.headers().add(DATE, dateFormatter.format(time.getTime()));
    }

    /**
     * Sets the Date and Cache headers for the HTTP Response
     *
     * @param response    HTTP response
     * @param fileToCache file to extract content type
     */
    private static void setDateAndCacheHeaders(FullHttpResponse response, File fileToCache) {
        SimpleDateFormat dateFormatter = new SimpleDateFormat(HTTP_DATE_FORMAT, Locale.US);
        dateFormatter.setTimeZone(TimeZone.getTimeZone(HTTP_DATE_GMT_TIMEZONE));

        // Date header
        Calendar time = new GregorianCalendar();
        response.headers().add(DATE, dateFormatter.format(time.getTime()));

        // Add cache headers
        time.add(Calendar.SECOND, HTTP_CACHE_SECONDS);
        response.headers().add(EXPIRES, dateFormatter.format(time.getTime()));
        response.headers().add(CACHE_CONTROL, "private, max-age=" + HTTP_CACHE_SECONDS);
        response.headers().add(
                LAST_MODIFIED, dateFormatter.format(new Date(fileToCache.lastModified())));
    }

    /**
     * Sets the content type header for the HTTP Response
     *
     * @param response HTTP response
     * @param file     file to extract content type
     */
    private static void setContentTypeHeader(FullHttpResponse response, File file) {
        MimetypesFileTypeMap mimeTypesMap = new MimetypesFileTypeMap();
        response.headers().add(CONTENT_TYPE, mimeTypesMap.getContentType(file.getPath()));
    }
}
